Will global warming change the way we sail?

Climate change is on the tip of everyone's tongue these days. From postmen to politicians and from your local deli to your local disc jockey, everyone and their brother are talking about climate change. Myriad articles have been written about the negative effect of global warming on ice caps, the positive effect of ice caps on global cooling, and the positively negative effect of said myriad articles on reforestation. Seemingly absent, however, from the ever-growing stacks of language and diagrams describing climate change and its causes is a discussion of the effect of climate change on sailing.

A recent study submitted to the Journal of Geophysical Research – Atmospheres by scientists at Iowa State University and Indiana State University (Pryor et. al, 2009) has caused quite a stir in the meteorological community, especially with those interested in harvesting energy from wind. In the study, the researchers found that surface wind speeds across the contiguous United States have decreased by around 0.75 percent per year since 1973. This decrease has been particularly prominent in the Northeast United States and over the Great Lakes.

Is it linked to global climate change? The authors hypothesized yes. The researchers admit there may be other reasons for this slowing trend (such as instrumentation flaws or local metropolitan buildup near observing stations-not insignificant factors!), but the assumption of climate change leading to slower winds is not new. Those who make that assumption draw upon the theory that a warmer Earth would reduce the temperature difference between the equator and the poles, reducing the strength of the midlatitude jet stream, and in turn, leading to slower surface winds. This is not the end of the theories, however, (I told you there are myriad articles).

Another line of thinking is that in a warming Earth scenario, land temperatures would increase faster than water temperatures, leading to greater thermal gradients along coastlines, leading to faster surface winds near the coast (Snyder et. al, 2008). Still another group of thought says that a warmer Earth in the upper atmosphere would lead to more storminess at the surface, thus causing both local increases and decreases of surface wind speed based on the location's proximity to the ever-increasing storms (Meehl et. al, 2007).

Most likely, all of the above theories are at least partially correct. The problem of nailing down a single all-encompassing theory comes when thinking on a global scale. Over land, whether or not winds change would depend greatly on the local geography and terrain. For example, a mountainous region could very well see an increase in wind speed with increasing surface temperature while a plains region saw a decrease in wind speed with the same surface temperature change. On the coast, warmer land than water could lead to stronger sea breezes, while offshore, surface winds could be slower due to a weaker jet stream. Of course, while this is happening, increased storminess would change each of those scenarios week to week. Confused yet?

The point is that every geographic region has its own unique climate and climatological tendencies. Global statements concerning local weather trends are very hard to make, and even harder to interpret and use in application. A global puzzle that varies locally requires both a global and local approach. In addition to the global modeling and statistics that are being done, and more applicably to the sailing community, one could focus on the recent climatology of a specific region during a specific period of interest. Such an approach to climate study would not only increase the accuracy and precision of any findings that are uncovered, but also increase the relevance to us as consumers of local weather and climate information. Armed with such information, the sailing community could make judgments on the near-term sail-ability of a venue, and gain tremendous insight into the venue's unique daily wind patterns.

Will climate change affect sailing? Sure, and it will vary from venue to venue. Will the effect be negative? I'm positive that no one knows yet. The real question is, what happens if the Earth cools? Better plant another forest.

Matthew Jones is chief of meteorological modeling for Sailing Weather Service (www.sailwx.com) and a nationally recognized and published expert in the application of high-resolution ensemble weather modeling systems customized for yacht racing teams.

References:

" Pryor, S.C., R.J. Barthelmie, D.T. Young, E.S. Takle, R.W. Arritt, D. Flory, W.J. Gutowski Jr., A. Nunes, and J. Roads, 2009: "Wind Speed Trends over The Contiguous United States," Journal of Geophysical Research, 114, D14105.

" Meehl, G.A., T.F. Stocker, W.D. Collins, P. Friedlingstein, A.T. Gaye, J.M. Gregory, A. Kitoh, R. Knutti, J.M. Murphy, A. Noda, S.C.B. Raper, I.G. Watterson, A.J. Weaver and Z.-C. Zhao, 2007: "Global Climate Projections." In: "Climate Change 2007: The Physical Science Basis." Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

" Synder, M.A., T. O'Brien, and L.C. Sloan, 2008: "Future Changes in Surface Winds in the Western U.S. Due to Climate Change," American Geophysical Union, Fall Meeting, 2008.